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Welcome to a new way of thinking about diving Understand that you are ALL novices again You will develop new skills for CCR diving including: –Attitudes –Disciplines –Awareness

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Introduction and Welcome Who the course is for and what you can expect to get out of it. COURSE PREREQUISITES –18 years of age –Logged 100+ dives –Nitrox and Advanced Nitrox training COURSE CREDENTIALS –To become qualified to dive the Inner Space Systems Megalodon on Air Diluent up to 40m/132ft with safety stops and 5 minutes max deco at 6m/ 20ft

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Introduction and Welcome What else can you expect to experience on this course? –Many new terms for CCR not used in OC or SCR diving –Change from a constant percentage Nitrox mix in OC to a variable percentage Nitrox mix with constant partial pressure in CCR mode –Computer controlled gas injection system on ascent causes accelerating bouyancy characteristics We need to think differently –Jump a billion years of evolutionary development An opportunity to almost evolve into a sea-going mammal with hours of sub-surface capability, and be back on land again for another fun filled experience

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TDI ISC Megalodon Rebreather Divers Course Section 2: The History and Development of Rebreathers

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The History and Development of Rebreathers Rebreathers in basic form have been around for over a century underwater, and longer for mine rescue work The earliest makes were pure oxygen devices The Englishman Henry Fleuss achieves a major milestone covering over 300 meters (1000 feet) underwater in the construction of the Severn railway tunnel a century ago Military rebreathers developed and used-Stealth

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The History and Development of Rebreathers The advent of readily available Nitrox to the recreational market fuelled the development of recreational nitrox SCR rebreathers Progress and need in the military theater saw the development of a number of electronic controlled CCR machines over the last two decades Some cave divers opted for passive mechanical SCR with no electronics Makes include the Electrolung; Cis Lunar; Drager Atlantis, Dolphin and Ray and Inspiration/Evolution. We see the advent of recreational CCR’s with the Inspiration in 1997, followed by Prism, Megalodon,Ouroboros, Optima and Kiss, and in 2005 the Evolution

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The History and Development of Rebreathers CONCEPTUAL REBREATHER DESIGN All need a scrubber for CO2 removal Pure Oxygen rebreather – no need for electronics in basic form just keep manually adding gas when loop volume falls Semi Closed SCR uses a known nitrox for loop addition Mechanical rebreathers use a fractional volume technique to refresh gas Either Passive by sucking in fresh gas when oxygen in the loop volume is depleted and a diaphragm regulator re-injects to bring loop volume back up, or Active – Constant flow rate of Nitrox to loop-vent excess

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The History and Development of Rebreathers Megalodon Rebreather Closed Circuit rebreathers (CCR) State of the art electronic controls Onboard sources of air and oxygen, scrubber, computer controlled variable Nitrox mixing Everything the recreational and technical diver needs

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Mechanics and basic functioning of the ISC Megalodon DIVERS LUNGS The motor that powers the gas around the rebreather gas loop The point of exchange for O 2 rich gas to the body and CO 2 rich gas from the body When we inhale, “clean” O 2 rich gas comes in from the Right. The flow is from the divers lungs through the mouthpiece to the Left

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Mechanics and basic functioning of the ISC Megalodon MOUTHPIECE and HOSES Mouthpiece and one-way mushroom valves control direction of gas flow Timing of gas flow is in sympathy with diver’s breathing pattern. Hoses are large bore. This reduces the work of breathing (WOB) (Always close the mouthpiece to prevent fluding)

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Mechanics and basic functioning of the ISC Megalodon EXHALATION COUNTERLUNG Counterlungs come from the factory as standard 5.5 ltr lungs made from highly durable cordura. (Neoprene Counter lungs can be order from ISC) Flexible breathing bag to contain gas from body Contains both the ADV, Mixed Gas By-pass (Additional Extra) and the Gas Loop Over Pressure Release Valve

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Mechanics and basic functioning of the ISC Megalodon THE CO 2 SCRUBBER (or Stack) Gas path is from the exhalation counterlung, through the T-piece down to the bottom of the CO 2 scrubber It fans out to a large bore axial flow through the scrubber to reduce gas velocity and increase “Dwell Time” for CO 2 removal The scrubber can is clear allowing the diver to see the Internal Dive Sorb.

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Mechanics and basic functioning of the ISC Megalodon THE SCRUBBER CARTRIDGE Designed to remove CO 2 from the gas loop. Situated on a spacer fitted with moisture pads to maintain air gap at bottom and soak up an moisture from the canister

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Mechanics and basic functioning of the ISC Megalodon The Scrubber Cartridge – continued Different scrubber makes can give different duration times due to different granule sizes Only designed to remove CO 2, not any other toxic compounds or contaminants in the breathing gas

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Mechanics and basic functioning of the ISC Megalodon SCRUBBER MATERIALS Have a defined shelf life time and in use up to 3 hours Effectiveness altered by time, temperature and moisture Sofnolime 797 grade recommended ( Other makes include Dragersorb and Sodasorb) Sofnolime is primarily a Sodium Hydroxide compound Needs proper packing to prevent CO2 channeling Efficiency is reduced by high gas flow rates (fast or skip breathing) or focused “channeling” characteristics In a properly assembled and properly functioning CCR system the CO2 scrubber is the “Achilles Heel”

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Mechanics and basic functioning of the ISC Megalodon SCRUBBER MANAGEMENT No partial filling of the scrubber. New full canister every time Do not empty scrubber into a bag and re-pack the scrubber later- new and used granules are then mixed Do not store partly used scrubber for more than a few days. The material absorbs CO 2 and grows mold

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Mechanics and basic functioning of the ISC Megalodon HANDSET CONTROLLER GENERALITIES Handset controllers are electronic – handle carefully There are two independent handset “controllers” on the ISC Megalodon and a HUD The main function of the primary controller is to control oxygen injections and display real time information to the diver The main function of the secondary controller is to provide the diver with a totally independant PO2 reading. Can be switched on and off separately

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THE PRIMARY HANDSET Redundant controller PPO 2 readings displayed to the diver Responsible for driving the Solinoid Requires independant Calibration. Primary Handset has a SSI (System Status Indicator +&- ) Must be switched on to have a chance to drive the oxygen solenoid Will give indications of battery health (load / no load), Cell health, Loop Temp, Outside Temp. Redundancy so that 1 controller can fail while the other allows you to safely exit the water Need to constantly be checking PPO 2 on the handset No Audio Alarm.

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HEADS UP DISPLAY (HUD) Three Colour Indicator powered by the secondary handset Can be disabled by the diver Adjustable Brightness control The HUD works by benchmarking setpoint 1.0 in ORANGE Cell Readings Higher than 1.0 are indicated by blinking GREEN Cell Readings Lower than 1.0 are indicated by blinking RED Each Cell will blink seperately with a short pause between each announcement. Mechanics and basic functioning of the ISC Megalodon

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THE CANNISTER “ LID” The electronic “brains” of the device Consisting of two indipendant Battery packs, wiring for the handsets and HUD, Oxygen Sensor Pod & Solinoid Great care should be taken when handling them For transport fully assemble rebreather or carry lid and handsets separately in a padded bag Treat it with the same care as a laptop Mechanics and basic functioning of the ISC Megalodon

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3 INDEPENDENT OXYGEN SENSORS 3 galvanic fuel cells each with a milli-volt output proportional to the oxygen exposure across their outer faces (breathing gas) The computers oxygen control averages all three Cells togethor to provide the PPO 2 This information is displayed to the diver both handsets Delicate pin connections Should never smell of “toxic” or other vapors Mechanics and basic functioning of the ISC Megalodon

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CONSTANT PPO2 GAS CONTROL Remember Dalton’s Law from Advanced Nitrox Pressure gas = FO 2 x Pressure At different depths (gas pressures) for a constant PPO 2 controller setting we will have a Nitrox mix that changes proportionally to pressure At any given depth we can calculate the Nitrox mix for any given PPO 2 setting Mechanics and basic functioning of the ISC Megalodon

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BATTERY COMPARTMENT Two independant battery compartments Sealed to atmospheric pressure Battery packs consist of either 2 x 3.6v Lithium cells or 5 Alkaline batterys supplied by ISC Mechanics and basic functioning of the ISC Megalodon WARNING! YOUR ELECTRONICS REQUIRE BATTERY POWER FOR OPERATION, ENSURE YOU HAVE ENOUGH POWER PRIOR TO EACH DIVE. CELLS READING 5.0V OR LESS SHOULD BE REPLACED

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CELL CONNECTORS These are delicate and covered with red or blue moisture caps with holes for pressure equalization Take great care not to damage wires or connectors if changing cells Check Mv output from cells before each dive Repalce your cells when Mv output falls below 9mv Mechanics and basic functioning of the ISC Megalodon Your Instructor will run through the correct procedure for calibrating the handsets and conducting the required linearity checks

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THE OXYGEN SUPPLY Dive tank switched on HP to SPG on front of Inhilation lung gives O 2 pressure LP hose feeds O 2 to the LID for the solenoid from the first stage regulator First stage regulator I/P is usually 10 bar with a range of between bar being acceptable You can choose dive tank size to suit your requirements Remember:- Rich mix Right, Lean mix Left Mechanics and basic functioning of the ISC Megalodon

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DILUENT GAS SUPPLY Need to use diluent below 6msw (20fsw) Manually add diluent on descent depressing the ADV “to equalize” the loop volume with pressure changes LP feeds to both the wing BCD and ADV Tank pressure is displayed on the SPG via HP hose over left shoulder Do not use for Drysuit inflation – use off board gas IP normally set to 10 Bar Mechanics and basic functioning of the ISC Megalodon WARNING The Megalodon CCR does not have on-board bailout, surficient bail out gas must be carried at all times.

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Physiology – A Reflection for the CCR Diver BASIC PREMISE We need to breathe clean (CO 2 and toxic gas free), appropriately oxygenated gas at all depths at all times to sustain life and to minimise DCS risk Appropriate nitrox mixes are delivered to the diver under software control according to the PPO 2 selected by the diver

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ADDITIONAL CONCEPTS Ascent must be controlled at less than 9m per minute as per normal diving practice. DSC and DCI risks still apply Dangers of hypoxia, hyperoxia, asphyxia and the insidious CCR carbon dioxide poisoning (hypercapnia) need examination Lets review sources of contamination of breathing loop NOAA toxicity guidelines apply for Whole Body and Pulmonary Toxicity Physiology – A Reflection for the CCR Diver

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CO 2 and HYPERCAPNIA Humans consume O 2 at a cellular level and generate CO 2 as a waste product Blood transports O 2 to the cells and removes CO 2 Blood exchanges CO 2 for O 2 at the lung Alveoli The urge to breathe is driven by the level of CO 2 retained in the body (blood and cells) With hypercapnia and elevated CO 2 levels, the breathing rate is increased (panting – dypsnea) to try to vent the lungs and alveoli Physiology – A Reflection for the CCR Diver

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HYPERCANPNIA SYMPTOMS Mild Symptoms –Headache –Anxiety and dizziness –Shortness of breath Severe Symptoms –Strong anxiety bordering on panic –Muscular difficulty and loss of dexterity in closing mouthpiece to bail out to OC –Diluent flush doesn’t seem to have any effect at first so divers often stop flushing when in fact they should continue flushing non-stop Physiology – A Reflection for the CCR Diver

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DEPTH VERSUS CO2 As depth increases, work of breathing increases to push more gas molecules around the breathing loop. More CO2 is generated as a result. As gas density of molecules increases the efficacy of the scrubber granules to absorb CO 2 across its surface decreases Physiology – A Reflection for the CCR Diver

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HYPEROXIA Too much oxygen results in O 2 toxicity risk Track O 2 toxicity per NOAA tables (see manual) At a default setpoint of 1.3, NOAA limit = 180 minutes - But 80% of that is 144 minutes Do not exceed 80% of CNS and OTU tables Need to monitor CNS% and OTU’s carefully on multi-dive days or multiple repeat dive days Physiology – A Reflection for the CCR Diver

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HYPOXIA Occurs if the PPO 2 drops below 0.16 at any time Real danger on ascent if solenoid fails Real danger if Oxygen tank is off or empty Symptoms can typically be breathlessness and panting, and lack of co-ordination Unconsciousness resulting in drowning can be sudden and without warning Physiology – A Reflection for the CCR Diver

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CNS TOXICITY AND OTU’s Real danger of convulsing and drowning if your CNS is not monitored properly Always know the PPO 2 in the loop and do a diluent flush to check any odd readings Track your CNS % and OTU’s on the NOAA tables in your manuals Physiology – A Reflection for the CCR Diver

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ASPHYXIA Like strangulation it is caused by a shortage of oxygen and buildup of CO 2 Restrictions in the breathing loop like a kinked mouthpiece hose can cause it Easily noticed early in a dive Ineffective or exhausted scrubber also can cause asphyxia Eventually results in unconsciousness Physiology – A Reflection for the CCR Diver

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Let’s Go Diving the Rebreather - Preparation EQUIPMENT ASSEMBLY and INSPECTION Preparation –Assemble the rebreather according to a checklist (refer to manual), initially under Instructor guidance –Be meticulous and do not get distracted

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WEIGHTING AND TRIM Ensure the unit is well weighted at the top. Add to the sides on the waistband to trim More weight needed if diving in a drysuit Let’s Go Diving the Rebreather - Preparation

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MACHINE CALIBRATION Absolutely critical part of the preparation process Always put in % of oxygen in the lid at 98% - all the air cannot be displaced from the lid Is the Mbar reading on the Megalodn handset are Automatically sensed Mbar readings are critical for altitude diving Watch the cell readings rise during calibration and check for any “slow” or “limited” cells Let’s Go Diving the Rebreather - Preparation Your Instructor will demonstrate correct calibration procedures

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GETTING THE FEEL OF THE MACHINE ON LAND Putting on the machine for a “dry dive” –Adjust straps to fit body correctly and tuck away loose ends –Power up and sequence handset control through to dive mode under guidance of Instructor –Select your Setpoint –Put on mask to prevent breathing through nose –Breathe on the machine while watching PPO2 readings on handsets listen for solenoid firing Let’s Go Diving the Rebreather - Preparation

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GENTLE EXERCISE Walk about with the rebreather on Simulate moderate exercise Notice breathing, rate increases, and solenoid firing more often than when at rest. Let’s Go Diving the Rebreather - Preparation

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INCREASED WORK LEVEL Jog in place for a couple of minutes, or do a few squats with the machine on to raise heart and respiratory rates Observe PPO 2 tracking, hear solenoid firing and notice little or no change in loop volume The student should still feel fine and have no CO 2 problems Let’s Go Diving the Rebreather - Preparation

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SETPOINT CHANGES Switch Setpoint when the PPO 2 rises observe PPO 2 on handset to ensure fuctionality Test how long it takes to breathe the loop back down to a PPO 2 of 0.4 at rest Let’s Go Diving the Rebreather - Preparation REMEMBER! There or no audio alarms for High or Low Oxygen on the Megalodon the diver should be monitoring the handsets at all times.

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OPEN CIRCUIT BAIL-OUT Close mouthpiece and come off the loop Switch to OC bailout – take 3 breaths, return to the loop and open mouthpiece Observe loop volume increase as O 2 is injected to bring PPO 2 back up to setpoint because of the air you introduce to the loop Let’s Go Diving the Rebreather - Preparation

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DILUENT FLUSH Inject diluent using the ADV Vent gas through by exhaling Repeat three times and observe reduction in PPO 2. Listen to solenoid firing. Let’s Go Diving the Rebreather - Preparation

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MANUAL GAS ADDITION Give a small squirt of O 2 with the manual addition button and observe the PPO 2 reading Repeat the exercise with diluent Repeat to get a “feel” for the addition buttons Let’s Go Diving the Rebreather - Preparation

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Let’s Go Diving the Rebreather – In the Water Rule No 1 If in doubt – bail out! Rule no 2 If something feels wrong – it is!

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DIVE PLANNING Select depth and time for a safe no-deco time Scrubber monitoring and planning (2.5 – 3 hour rule) Gas volume planning – enough for a bail-out Oxygen planning – CNS% and OTUs Is this a repetitive dive? Thermal protection appropriate for conditions and duration of dive Brief team, do ABCs and enter the water under guidance of your Instructor Let’s Go Diving the Rebreather – In the Water

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FIRST IMPRESSIONS IN THE WATER Silence Bubble-free Listen for the solenoid firing Check PPO 2 on the handsets every minute Dynamic bouyancy change caused by computer- controlled oxygen Unit is bouyant at shoulder level due to air volume in counterlungs and hoses Add weight at the top for trim Remember – no matter how experienced you are on OC, you are now a beginner again Let’s Go Diving the Rebreather – In the Water

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EARLY TECHNIQUE POINTERS Do not expect to get it right first time Try to keep the loop volume at a minimum for comfort Keep a steady depth level Try to maintain a horizontal, neutral bouyancy, attitude while swimming Use vertical attitude only when testing skills under instructor guidance Be generous with weighting (1 or 2kg over) Let’s Go Diving the Rebreather – In the Water

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HIGH OXYGEN DRILLS Open circuit bailout Use of diluent flush to drop PPO2 Closing oxygen tank if solenoid fails open Let’s Go Diving the Rebreather – In the Water

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MENU MODE DRILLS Sequencing through menu commands in water to become familiar with functionality Changing Setpoints Observe System Monitor Observe SSI indicator Let’s Go Diving the Rebreather – In the Water

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Avoiding Rebreather incidents – Safe Diving All the training in the world is useless if you do not adopt the following as your personal mantra for CCR Diving: –Safe Attitude –Safe and enhanced Awareness –Safe and structured Discipline

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Avoiding Rebreather incidents – Safe Diving Properly assemble and check according to a check list Do not get distracted during calibration Do all the pre-dive checks and then “go live” for a short “dry-dive” to pre-breathe prior to entering water in order to ensure dynamic functionality of the machine REMEMBER DURING PRE-DIVE PREPARATION

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Avoiding Rebreather incidents – Safe Diving REMEMBER AT THE SURFACE NEVER switch off the handsets or tanks at the surface above deep water Only shut down after equipment has been taken off You still need to watch your PPO 2 if you breathe on the loop at the surface It’s the best snorkel you ever bought!!!

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Avoiding Rebreather incidents – Safe Diving REMEMBER AFTER THE DIVE Gas up again for the following dive Check and replace batteries/scrubber as necessary Disinfect and clean as necessary Conduct all other system checks to ensure correct functionality of cells and handsets Log your dives

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Avoiding Rebreather incidents – Safe Diving TDI Training and Manufacturers Manuals –Errors and troubleshooting are well documented for reference –Maintain your own service log for batteries/scrubber and other service needs –Document your rebreather experiences